One vertex per element, one color per generator, with an edge from x to x·s.
(2,5)(6,8)(9,10)(11,18)(12,15)(13,17)(14,22)(16,20)(19,24)(21,23)(25,26,28,32,29,31,35,38)(27,30,34,37,33,36,39,40)(1,2)(3,6)(4,5)(7,8)(11,19)(14,23)(18,24)(21,22)(25,27)(26,30)(28,34)(29,33)(31,36)(32,37)(35,39)(38,40) involution — undirected(1,3,4,7)(2,6,5,8)(9,11,20,21,13,19,12,22)(10,14,15,24,17,23,16,18)(27,33)(30,36)(34,39)(37,40)(2,5)(6,8)(9,12,13,20)(10,15,17,16)(11,21,19,22)(14,18,23,24)(26,31)(30,36)(32,38)(37,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.